A third-generation mobile communication system carries out (1) RAKE combining processing, (2) physical channel decoding processing and (3) transport channel decoding processing, in that order, and then carries out error correcting decoding processing. The RAKE combining processing refers to processing of separating a received signal in which preceding waveforms and delayed waveforms affected by independent fading variations with different delay times in a multipath transmission path are superimposed on one another into the preceding waveforms and delayed waveforms, assigning weights to the waveforms with a uniform delay time and performing a maximum-ratio combining and it is intended to obtain a diversity effect. On the other hand, the physical channel decoding processing refers to processing of carrying out in-frame deinterleaving, etc. on a signal for each RAKE-combined physical channel data string and dividing the signal into transport channels. The transport channel decoding processing is processing of carrying out deinterleaving, rate matching and error correcting decoding on signals of divided transport channel data strings over a plurality of frames.
For a radio communication system, it is important to reduce decoding errors of a received signal to improve communication quality.